Assessing Exposures & Health Outcomes

With respect to exposures, two types of exposure data are required: those that pertain to the ambient environment (e.g., workplace air) and those that pertain to the internal environment of the worker (e.g., health surveillance). To be of use in risk assessment, each must be linked to the other. Workplace surveillance (air monitoring) is discussed in detail in Chapter 7. Human health surveillance is discussed below.

Health surveillance may be used to evaluate an individual’s health prior to, during, and at termination of employment. Occasionally, it also may be used during retirement. A properly executed health surveillance plan can be useful in determining changes in the health status of an employee. However, considerable clinical skill and judgment will be required to assess whether any change can be attributed to workplace conditions.

In countries where it is possible to obtain mortality or cancer registry data, follow-up of personnel who have left the industry is strongly recommended so that information on the eventual cause of death can be made available for possible epidemiological research. Likewise, employers are advised to retain copies of death certificates of all personnel who die while still employed or as pensioners. Special efforts to ascertain the vital status of workers who have “quit” the workforce are recommended (Verma et al., 1996).

In addition to mortality data, morbidity data may also be obtained in certain countries as part of voluntary data collection programs, such as the United Kingdom’s Occupational Physicians

Reporting Activity (OPRA) program, or as part of a national, state, or provincial accident/disease registry or workers’ compensation program. Such data may be useful in identifying occupational disease trends (e.g., cases of occupational asthma) within an industry sector.

The decision to commence a surveillance program has many biological, social, and legal considerations that must be taken into account. As noted in the introduction, in some countries, implementation of a health surveillance program is obligatory. In such instances, advice should be sought from the relevant local/national authority. Further legal considerations may include requirements for medical recordkeeping. In some countries, medical records are required to be kept for the duration of a worker’s employment plus an additional prescribed time (usually 30 to 40 years).

Issues such as the invasiveness, sensitivity, and accuracy of testing procedures should also be considered, and any potential health benefits of these procedures should be weighed against the risks of performing such tests. Where possible, tests should be designed to investigate the quantitative relationship between the ambient workplace exposure, the biological measurement of the exposure, and the health effect of concern. The rights of workers with respect to issues such as confidentiality and compulsory examination must be carefully considered. Any health data gathered and recorded should be subject to rigorous quality control. The International Council on Mining and Metals has developed a Guide to Data Gathering Systems for the Risk Assessment of Metals (ICME, 1999). Useful information regarding the data needs of a health surveillance program is provided within this guide.

In structuring a health surveillance program, consideration ideally should be given to the components discussed below.